Size Effects on Diffusion Processes within Agarose Gels

Abstract

To investigate diffusion processes in agarose gel, nanoparticles with sizes in the range between 1 and 140 nm have been tested by means of fluorescence correlation spectroscopy. Understanding the diffusion properties in agarose gels is interesting, because such gels are good models for microbial biofilms and cells cytoplasm. The fluorescence correlation spectroscopy technique is very useful for such investigations due to its high sensitivity and selectivity, its excellent spatial resolution compared to the pore size of the gel, and its ability to probe a wide range of sizes of diffusing nanoparticles. The largest hydrodynamic radius (R(c)) of trapped particles that displayed local mobility was estimated to be 70 nm for a 1.5% agarose gel. The results showed that diffusion of particles in agarose gel is anomalous, with a diverging fractal dimension of diffusion when the large particles become entrapped in the pores of the gel. The latter situation occurs when the reduced size (R(A)/R(c)) of the diffusing particle, A, is >0.4. Variations of the fractal exponent of diffusion (d(w)) with the reduced particle size were in agreement with three-dimensional Monte Carlo simulations in porous media. Nonetheless, a systematic offset of d(w) was observed in real systems and was attributed to weak nonelastic interactions between the diffusing particles and polymer fibers, which was not considered in the Monte Carlo simulations.

Methods to determine the interactions of micro- and nanoparticles with mucus

“…Here the mucin fibres are undergoing continuous association and disassociation and the network as a whole undergoes elastic behavior resulting in the formation and collapse of aqueous cages surrounded by mucin fibres [51]. As such there will be significant potential for particle-gel interactions within mucus the probability of which increases as a function of time [52]. Accordingly, how the diffusion of individual particle changes with time not only provides information on the kinetics of movement but also the nature of movement, e.g.…”

Controlled antibody release from gelatin for on-chip sample preparation

“…[36][37][38][39][40] Four types of antibody and antibody fragments with different molecular weights (MWs) were chosen to study the influence of the reagent size on the release. The radii of the antibodies were calculated using nm 0.066 Da…”

New insights into diffusion in 3D crowded media by Monte Carlo simulations: effect of size, mobility and spatial distribution of obstacles

“…In order to give only a few examples, FRAP experiments have revealed anomalous diffusion of dextrans [17][18]23 , of proteins in cytoplasm 19,[21][22]25,33 and of proteins in dextrans 35 . FCS experiments have also shown anomalous diffusion of nanoparticles with different sizes in agarose gel 26 , of dextrans in HeLa cell cytoplasm 28 , of proteins in three-dimensional crowded media 27,31 , of Alexa488 lightemitting particles in extracellular matrices 32 , respective of the inert gold nanoparticles in the cytoplasm and nucleoplasm under various stress conditions 34 .…”

“…A great deal of information about motion of molecules in living cells has been obtained from intracellular measurements using different experimental techniques 13,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] and from simulations 14,[36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] . Experimental data are usually obtained by fluorescence recovery after photobleaching (FRAP) and fluorescence correlation spectroscopy (FCS) techniques.…”